14万字 | 400多道JavaScript 面试题及详细答案12（建议收藏）

var namespaceOne = {
function func1() {
console.log("This is a first definition");
}
}
var namespaceTwo = {
function func1() {
console.log("This is a second definition");
}
}
namespaceOne.func1(); // This is a first definition
namespaceTwo.func1(); // This is a second definition

(function() {
function fun1(){
console.log("这是第一个定义");
} fun1();
}());
(function() {
function fun1(){
console.log("这是第二个定义");
} fun1();
}());

{
let myFunction= function fun1(){
console.log("这是第一个定义");
}
myFunction();
}
//myFunction(): ReferenceError: myFunction 未定义。
{
let myFunction= function fun1(){
console.log("这是第二个定义");
}
myFunction();
}
//myFunction(): ReferenceError: myFunction 未定义。

function loadAssets(filename, filetype) {
if (filetype == "css") { // External CSS file
var fileReference = document.createElement("link")
fileReference.setAttribute("rel", "stylesheet");
fileReference.setAttribute("type", "text/css");
fileReference.setAttribute("href", filename);
} else if (filetype == "js") { // External JavaScript file
var fileReference = document.createElement('script');
fileReference.setAttribute("type", "text/javascript");
fileReference.setAttribute("src", filename);
}
if (typeof fileReference != "undefined")
document.getElementsByTagName("head")[0].appendChild(fileReference)
}

$(document).ready(function(){ // 它选择文档并在页面加载时应用该功能
alert('Welcome to jQuery world');
});

var name = 'Haiyong';
function myFunc() {
var name = 'Nick';
var name = 'Abraham'; // 在同一功能块中重新分配
alert(name); // Abraham
}
myFunc();
alert(name); // Haiyong

let name = 'Haiyong';
function myFunc() {
let name = 'Nick';
let name = 'Abraham'; // 未捕获的语法错误：标识符"name"已被声明
alert(name);
}
myFunc();
alert(name);

var user1 = 'Haiyong';
 var skill1 = 'JavaScript';
 var experience1 = 15;
 var user2 = 'CSDN';
 var skill2 = 'JavaScript';
 var experience2 = 5;
 function myInfoTag(strings, userExp, experienceExp, skillExp) {
   var str0 = strings[0]; // "Mr/Ms. "
   var str1 = strings[1]; // " is a/an "
   var str2 = strings[2]; // "in"
   var expertiseStr;
   if (experienceExp > 10){
     expertiseStr = 'expert developer';
   } else if(skillExp > 5 && skillExp <= 10) {
     expertiseStr = 'senior developer';
   } else {
     expertiseStr = 'junior developer';
   }
   return ${str0}${userExp}${str1}${expertiseStr}${str2}${skillExp};
 }
 var output1 = myInfoTag`Mr/Ms. ${ user1 } is a/an ${ experience1 } in ${skill1}`;
 var output2 = myInfoTag`Mr/Ms. ${ user2 } is a/an ${ experience2 } in ${skill2}`;
 console.log(output1);// Mr/Ms. Haiyong is a/an expert developer in JavaScript（是一位 JavaScript 专家开发人员）
 console.log(output2);// Mr/Ms. CSDN is a/an junior developer in JavaScript（

var calculationString = String.raw `The sum of numbers is \n${1+2+3+4}!`;
  console.log(calculationString); // The sum of numbers is 10
如果不使用原始字符串，将通过多行显示输出来处理换行符序列
  var calculationString = `The sum of numbers is \n${1+2+3+4}!`;
  console.log(calculationString);
  // The sum of numbers is
  // 10
此外，原始属性可用于标记函数的第一个参数
  function tag(strings) {
     console.log(strings.raw[0]);
  }

var [one, two, three] = ['JAN', 'FEB', 'MARCH'];
 console.log(one); // "JAN"
 console.log(two); // "FEB"
 console.log(three); // "MARCH"
并且您可以使用解构赋值获取对象的用户属性，
 var {name, age} = {name: 'Haiyong', age: 22};
 console.log(name); // Haiyong
 console.log(age); // 22

//ES6
var x = 10, y = 20
obj = { x, y }
console.log(obj); // {x: 10, y:20}
//ES5
var x = 10, y = 20
obj = { x : x, y : y}
console.log(obj); // {x: 10, y:20}